Cordless power tools provide many advantages to traditional corded power tools. In particular, cordless tools provide unmatched convenience and portability. An operator can use a cordless power tool anywhere and anytime, regardless of the availability of a power supply. In addition, cordless power tools provide increased safety and reliability because there is no cumbersome cord to maneuver around while working on the job, and no risk of accidently cutting a cord in a hazardous work area.
However, conventional cordless power tools still have their disadvantages. Typically, cordless power tools provide far less power as compared to their corded counterparts. Today, operators desire power tools that provide the same benefits of convenience and portability, while also providing similar performance as corded power tools.
Brushless DC (BLDC) motors have been used in recent years in various cordless power tools. BLDC motors offer many size and power output advantages over universal and permanent magnet DC motors. BLDC motors are electronically-controller via a programmable controller, and thus do not suffer from many mechanical failures associated with universal motor.
However, BLDC motors may be prone to some software failure associated with software bugs, contaminated routing and/or wiring, or a faulty micro-controller chip. What is needed is a mechanism to protect the power tool from such failures.
In addition, in cordless power tools operated via a battery pack, the over-discharge of the battery cells can permanently damage the power tool. This can occur when, for example, the tool trigger is depressed by accident for an extended period of time, causing current leakage to the various power tool components. What is needed is a mechanism that protects the battery pack from current leakage that cause the battery cells from over-discharge.